EP3939960A1 - Method for the recovery of diamines from aqueous mixtures - Google Patents

Abstract

The invention relates to a process for obtaining at least one aliphatic, araliphatic or cycloaliphatic diamine from a mixture containing at least 35% by weight of water and 0.2 to 60% by weight of the at least one aliphatic, araliphatic or cycloaliphatic diamine by extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile to obtain an aqueous phase containing water and a portion of the at least one dicarboxylic acid dinitrile and an organic phase containing a further portion of the at least one dicarboxylic acid dinitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine.

Description

The invention relates to a process for obtaining at least one aliphatic, araliphatic or cycloaliphatic diamine from an aqueous mixture and the use of dicarboxylic acid dinitriles for extracting at least one aliphatic, araliphatic or cycloaliphatic diamine from an aqueous mixture and an organic phase obtainable by this process containing at least one Dicarboxnitrile, at least one aliphatic, araliphatic or cycloaliphatic diamine and water and the use of such an organic phase as a starting material in a hydrogenation reaction.

Aliphatic, araliphatic or cycloaliphatic diamines are important starting materials for the production of polymers. They can first be converted into diisocyanates, which are then converted into polyurethanes, polyureas, polythiourethanes or polyisocyanurates. Another important application of diamines is the production of polyamides by polycondensation of the diamine with dicarboxylic acids.

Polyamides are produced, for example, by heating aqueous solutions of diamines and dicarboxylic acids. The solution is heated under pressure, the pressure being kept constant by releasing excess water vapor. In order to complete the polycondensation, the water must be completely removed from the reaction mixture. Since the diamine components are volatile in steam, this results in a diamine-containing waste water that has to be treated in a complex manner.

In CN101993178(A ) such a method for waste water treatment of waste water containing 1,6-hexanediamine is described, which includes an anaerobic and an aerobic treatment of the waste water. A disadvantage of the process is that the 1,6-hexanediamine contained is destroyed in the process and is thus prevented from further material use.

For the production of hexamethylene diisocyanate from 1,6-hexanediamine, certain requirements for the diamine are known. For example, describes the CN103922969B that low-boiling secondary components such as tetrahydroazepine, 1-amino-2-cyano-1-cyclopentene or 6-aminocapronitrile should only be present to a very small extent. In the EP2060560B1 describes in general that particularly light-colored isocyanates can be prepared from amines whose PRI value, ie the content of polarographically reducible compounds, is less than 60 mol ppm.

Other aliphatic diamines are obtained, for example, by hydrogenation or reductive amination (also referred to as aminating hydrogenation) of corresponding oxygen-containing compounds. This can, for example, as in WO2012076315A1 described, the reductive amination of 3-cyano-3,5,5-trimethylcyclohexanone to 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA) or the hydrogenation of nitro-containing Links. In addition to the desired diamine, this always produces water, so-called water of reaction. This can then be separated from the amine in various ways and then occurs as a waste water stream containing diamine. If there is a miscibility gap or this can be brought about by adding other substances (e.g. salts or solvents), it is advisable to first carry out a phase separation and later to further dry the organic amine phase by distillation. If there is no miscibility gap, all of the water to be removed is usually removed by distillation, with part of the diamines generally going over with the distillate.

Another source of aqueous solutions of aliphatic, araliphatic or cycloaliphatic diamines is the recycling of polyurethanes based on the corresponding diisocyanates or of polyamides, which is playing an increasingly important role in industry. If these plastics are chemically hydrolyzed, aqueous solutions of aliphatic, araliphatic or cycloaliphatic diamines are obtained, from which the aliphatic, araliphatic or cycloaliphatic diamines have to be recovered.

1,5-Pentanediamine is produced industrially using biotechnology and occurs as an aqueous solution. In EP2684867A1 describes, for example, a process for preparing 1,5-pentanediamine in which the diamine is extracted from the aqueous phase in a liquid phase extraction. Halogen-free aliphatic solvents, preferably unbranched alcohols with 4 to 7 carbon atoms, are recommended as extraction agents. These extraction agents then have to be laboriously separated from the product.

Also the EP3235804A1 describes an extraction of 1,5-pentanediamine from an aqueous phase. Following the extraction, however, a reduction is carried out here in order to break down 2,3,4,5-tetrahydropyridine, which is held responsible for subsequent discoloration of the polyamides produced from the 1,5-pentanediamine. For this reason, the extraction agent is required to behave inertly in the chemical hydrogenation. Again, alcohols such as ethanol or butanol are preferred as extractants.

Proceeding from this prior art, the object of the present invention was to provide an economically and ecologically more sensible process for obtaining aliphatic, araliphatic or cycloaliphatic diamines from an aqueous mixture.

This object was achieved by a process for obtaining at least one aliphatic, araliphatic or cycloaliphatic diamine from a mixture containing at least 35% by weight of water and 0.2 to 60% by weight of the at least one aliphatic, araliphatic or cycloaliphatic diamine by extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile to obtain an aqueous phase containing water and a portion of the at least one dicarboxylic acid dinitrile and an organic phase containing a further portion, preferably the remaining portion of the at least one dicarboxylic acid dinitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine.

According to the invention, the expressions “comprising” or “containing”, “consisting essentially of” and particularly preferably “consisting of” preferably mean.

In the context of the present invention, the content of organic compounds relates, unless otherwise stated, to values determined by gas chromatography. The person skilled in the art is familiar with the quantitative evaluation of gas chromatograms, if appropriate with the aid of an internal standard. Any methods required to determine the water content are also known to those skilled in the art. The methods of the prior art can also be used within the scope of the present invention. In case of doubt, the water content determined by Karl Fischer titration is decisive. The presence of amines can lead to sluggish endpoints. In such cases, the value determined by Karl Fischer titration after buffering with anhydrous benzoic acid is decisive. The method of buffering with benzoic acid is also known to those skilled in the art. For Karl Fischer titration in general, see Jander, Jahr, Maßanalyse, 17th ed., de Gruyter, Berlin (2009), pp. 279 to 282 ).

"At least one" as used herein refers to 1 or more, for example 2, 3, 4, 5, 6, 7, 8, 9 or more. In the context of components of the compounds described herein, this specification does not refer to the absolute amount of molecules, but to the type of component. "At least one aliphatic, araliphatic or cycloaliphatic diamine" therefore means, for example, that only one type of diamine or several different types of diamines can be present, without giving any information about the amount of the individual compounds.

Numerical values given herein without decimal places refer to the full stated value with one decimal place. For example, "99%" means "99.0%".

Numerical ranges given in the format "in/from x to y" include the stated values. Where multiple preferred numeric ranges are given in this format, it is understood that any ranges resulting from the combination of the different endpoints are also included.

The at least one dicarboxylic acid dinitrile is preferably a dicarboxylic acid dinitrile of the formula (I),

NC-R-CN (I),

where R is an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 4 to 8 carbon atoms, or an aryl group having 6 carbon atoms. Mixtures of such dicarboxylic acid dinitriles can also be used according to the invention.

In a preferred embodiment of the invention, dicarboxnitriles of the formula (I) are used, where R is a straight-chain or branched alkyl radical having 2 to 6 carbon atoms, an alkenyl radical having 4 carbon atoms or an aryl radical having 6 carbon atoms.

In a particularly preferred embodiment, the at least one dicarboxylic acid dinitrile is selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, methylglutaronitrile, ethylsuccinonitrile and methyleneglutaronitrile.

In a very particularly preferred embodiment, the at least one dicarboxylic acid dinitrile is selected from the group consisting of glutaronitrile, methyleneglutaronitrile and adiponitrile.

The preparation of such dicarboxylic acid dinitriles is known to those skilled in the art. Industrially, it takes place, for example, by adding hydrogen cyanide to suitable starting materials, such as acrylonitrile or butadiene, or by catalytic oxidation of alkenes and ammonia with air. Reactions of cyanogen chloride, for example with acetonitrile to give malonitrile, have also been described as ways of preparing dicarboxnitriles, or substitution reactions of haloalkanes with alkali metal cyanides.

Glutaronitrile for the extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile can basically be prepared in any manner known to those skilled in the art. It can be prepared, for example, by reacting a solution of 1,3-dichloropropane with potassium cyanide. For isolation, the glutaronitrile can then, for example, first be extracted in a liquid-liquid extraction with water and methylene chloride. If necessary, the water can be mixed with further salts, for example sodium chloride or potassium chloride, in order to improve the phase separation. After the phases have been separated, the glutaronitrile-containing organic phase can be worked up by distillation, optionally after drying, in order to obtain the glutaronitrile in pure form.

Methyleneglutaronitrile for the extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile can basically be prepared in any way known to the person skilled in the art. It can be obtained, for example, in a catalytic dimerization of acrylonitrile in the presence of tricyclohexylphosphine or of metal halides and trialkylamines. The methyleneglutaronitrile is worked up, for example, as in column 3, line 35 to column 4, line 41 of US4422981 described, extractively in the presence of water. The organic phase can later be subjected to a vacuum distillation, for example, in order to prepare the methyleneglutaronitrile in pure form. In such a method can also be the treatment of the extraction of at least one aliphatic, araliphatic or cycloaliphatic diamine with at least a dicarboxylic acid dinitrile accumulating, methyleneglutaronitrile-containing waste water stream well integrated into the process.

Adiponitrile for the extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile can in principle be prepared in any manner known to those skilled in the art. On the one hand, the catalytic hydrocyanation of 1,3-butadiene and the dimerization of acrylonitrile have established themselves industrially. In the dimerization of acrylonitrile, a distinction is made between catalytic dimerization, in which hexenedinitrile is initially formed, which is then hydrogenated, and electrochemical hydrodimerization, which leads directly to adiponitrile. For the extraction according to the invention of the at least one aliphatic, araliphatic or cycloaliphatic diamine, preference is given to using an adiponitrile which has been prepared by electrochemical hydrodimerization. In this process, the treatment of the adiponitrile-containing waste water stream obtained during the extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with adiponitrile can also be easily integrated into the process.

Mixtures containing at least 35% by weight of water and 0.2 to 60% by weight of at least one aliphatic, araliphatic or cycloaliphatic diamine are obtained, as described above, in very different chemical processes, for example as a waste water stream or as a crude product stream. Particularly suitable for the process according to the invention are those mixtures which contain at least one aliphatic, araliphatic or cycloaliphatic diamine of ≦40% by weight, preferably ≦25% by weight, particularly preferably ≦12% by weight, based on the total mass the mixture. At the same time, the content is preferably ≧0.5% by weight, preferably ≧1% by weight and particularly preferably ≧2% by weight, based on the total mass of the mixture. At higher contents of aliphatic, araliphatic or cycloaliphatic diamines, the distillative treatment of the mixture to separate off the aliphatic, araliphatic or cycloaliphatic diamines becomes more important for economic reasons, while at lower contents the separation of the at least one diamine from the mixture loses its economics. In addition to the at least one aliphatic, araliphatic or cycloaliphatic diamine and water, the aqueous phase generally also contains small amounts of other compounds. These can be, for example, alcohols, glycols, amino alcohols, imines, carbohydrates, nitro compounds, inorganic or organic acids, carboxylic acid esters, carboxamides, inorganic or organic bases, in particular primary or secondary amines, polarographically reducible compounds such as 2,3,4,5-tetrahydropyridine, be tetrahydroazepine, 1-amino-2-cyano-1-cyclopentene or 6-aminocapronitrile, urethanes or ureas.

The aliphatic, cycloaliphatic or araliphatic diamine is preferably selected from the group consisting of 1,4-butanediamine, neopentanediamine, 1,5-pentanediamine (PDA), 1,5-diamino-2-methylpentane, 1,5-diamino-2- butyl-2-ethylpentane, 1,6-hexanediamine (HDA), 2,5-diamino-2,5-dimethylhexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 1,4-diaminocyclohexane, 2,4-diamino-1-methylcyclohexane, 2,6-diamino-1-methylcyclohexane, m-hexahydroxylylenediamine , 1,6-diamino-2,2,4-trimethylhexane, 1,6-diamino-2,4,4-trimethylhexane, 2,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, bis(aminomethyl)bicyclo[2.2 .1]heptane (NBDA), 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane and m-xylylenediamine (XDA).

Preferably the aliphatic, cycloaliphatic or araliphatic diamine is an aliphatic diamine selected from the group consisting of 1,4-butanediamine, 1,5-pentanediamine, 1,5-diamino-2-methylpentane and 1,6-hexanediamine. Most preferably, the aliphatic diamine is 1,5-pentanediamine or 1,6-hexanediamine.

According to the invention, the mixture containing at least 35% by weight of water and 0.2 to 60% by weight of the at least one aliphatic, araliphatic or cycloaliphatic diamine is fed to an extraction in which the at least one aliphatic, araliphatic or cycloaliphatic diamine contained in the mixture is brought into contact with at least one dicarboxylic acid dinitrile and extracted in this way. During the extraction, an aqueous phase containing water and a portion of the at least one dicarboxylic acid dinitrile and an organic phase containing a further portion, preferably the remaining portion, of the at least one dicarboxylic acid dinitrile, the at least one aliphatic, araliphatic or cycloaliphatic diamine and water are formed and separated from one another . The separated organic phase preferably contains 75 to 100%, particularly preferably 95 to 100% and very particularly preferably 98 to 99.99% of the at least one aliphatic, araliphatic or cycloaliphatic diamine originally contained in the aqueous mixture.

The organic phase, ie the extract, containing the one further subset, preferably the remaining subset, of the at least one dicarboxylic acid dinitrile, the at least one aliphatic, araliphatic or cycloaliphatic diamine and water is also a subject of the invention. The water content of the extract results essentially from the solubility of water in the at least one dicarboxylic acid dinitrile under the extraction conditions. The water content of the extract is preferably ≦25% by weight, particularly preferably ≦12% by weight, very particularly preferably ≦8% by weight and most preferably ≦6% by weight of water, based on the total mass of the extract. As a rule, the water content of the extract is not less than 0.2% by weight, preferably not less than 0.5% by weight, particularly preferably not less than 1% by weight and very particularly preferably not less than 2% by weight of water based on the total mass of the extract.

The extraction preferably takes place as a liquid-liquid extraction, in which the mixture containing the at least one aliphatic, araliphatic or cycloaliphatic diamine is brought into contact with the at least one dicarboxylic acid dinitrile. This can be done as a batch, semi-continuous or continuous, where the two phases are mixed.

All methods and apparatus known to those skilled in the art, such as mixer-settlers or extraction columns, can be used for the extraction. The extraction can be carried out in one or more stages in co-current or counter-current. The extraction is preferably carried out in countercurrent, a multi-stage extraction in countercurrent being particularly preferred.

The two phases can be mixed in any manner, for example static mixers, mixing nozzles, stirrers or mixing pumps can be used. In order to reduce the necessary separation and residence times, the separation apparatus (separators) used can be provided with coalescence aids such as knitted fabrics, plates or packing. It is also possible to bring about the phase separation in a centrifuge or to improve it by applying an electric field.

Suitable devices for the extraction are known to those skilled in the art. Mixers/settlers or extraction columns are preferably used. The extraction is generally carried out at temperatures from 10 to 110.degree. C., preferably from 20 to 80.degree. C. and particularly preferably from 22 to 45.degree. If a dicarboxnitrile solid at room temperature, such as succinonitrile, is used for the extraction, it is advantageous to carry out the extraction at an elevated temperature, preferably in the range from 60 to 80° C., in order to avoid crystallization of the dicarboxnitrile solid at room temperature. In many cases, but especially when using succinonitrile as the extraction agent, the presence of a salt is advantageous for improving phase separation. The pressure is generally from 1 to 6 bar(a), preferably from 1 to 3 bar(a) and particularly preferably from 1 to 1.2 bar(a). The extraction therefore very particularly preferably takes place at a temperature of 25 to 45° C. and a pressure of 1 to 1.2 bar(a).

In a further preferred embodiment of the invention, the mixture containing the at least one aliphatic, araliphatic or cycloaliphatic diamine is extracted 1 to 30 times, preferably 1 to 10 times and particularly preferably 2 to 8 times with the at least one dicarboxylic acid dinitrile or in an extraction column with a corresponding one Number of extraction stages extracted. The volume ratio of the mixture containing the at least one aliphatic, araliphatic or cycloaliphatic diamine to the at least one dicarboxylic acid dinitrile is in the range from 6:1 to 1:12, preferably in the range from 2:1 to 1:6 and particularly preferably in the range from 1: 1 to 1:3. In order to adjust the volume ratios, it is also possible to circulate part of the aqueous and/or organic phase obtained in the extraction. The recirculation can take place in the same extraction stage or in another, further upstream extraction stage.

The extraction preferably takes place in an alkaline environment, ie at a pH>7, preferably at a pH≧9, particularly preferably at a pH≧10 and very particularly preferably at a pH≧11 the setting of the alkaline environment by adding an inorganic base, preferably by adding a or more alkali metal hydroxides, particularly preferably by adding sodium hydroxide. The base can be added in pure form or as a solution, preferably as an aqueous solution.

In this way, with the aid of the process according to the invention, 75 to 100%, preferably 95 to 100% and particularly preferably 98 to 99.99% of the at least one aliphatic, araliphatic or cycloaliphatic diamine originally contained in the aqueous mixture are extracted from the aqueous phase.

The aqueous phase obtained after the extraction contains no or only small amounts of the at least one aliphatic, araliphatic or cycloaliphatic diamine and a small amount of the at least one dicarboxylic acid dinitrile. The content of dicarboxylic acid dinitrile depends, inter alia, on the dicarboxylic acid dinitrile and its solubility in water and on the process conditions chosen, in particular the temperature. It is, for example, between 0.1 and 20% by weight, preferably between 0.2 and 10% by weight and particularly preferably between 1 and 5% by weight. The content of aliphatic, araliphatic or cycloaliphatic diamine in the aqueous phase depends, inter alia, on the original content of aliphatic, araliphatic or cycloaliphatic diamine in the mixture to be extracted and can be, for example, up to 5.00% by weight at high original contents. The content of aliphatic, araliphatic or cycloaliphatic diamine in the aqueous phase is preferably between 0.0005 and 0.5% by weight, particularly preferably between 0.001 and 0.2% by weight and very particularly preferably between 0.001 and 0.1 % by weight based on the total mass of the aqueous phase, where the amine can be present as a free amine or in the form of an acidic salt. This aqueous phase can now preferably be used elsewhere, for example for an extraction. Alternatively, it can, for example, be pre-cleaned by distillation and then fed into a biological waste water treatment.

In a preferred embodiment of the invention, the aqueous phase, optionally after carrying out further intermediate steps such as neutralization, filtration or desalination, is used in a process for preparing the dicarbodinitrile corresponding to the dicarbodinitrile contained in the aqueous phase in an extraction step. For example, an aqueous phase containing glutaronitrile is preferably used in a liquid-liquid extraction of glutaronitrile in a process for preparing glutaronitrile, an aqueous phase containing methyleneglutaronitrile is preferably used in a liquid-liquid extraction in a process for preparing methyleneglutaronitrile, an aqueous phase containing adiponitrile preferably in a liquid-liquid extraction in a process for the production of adiponitrile, and so on.

For example, as described above, the purification of glutaronitrile may involve a liquid-liquid extraction in the presence of water and an organic solvent such as methylene chloride. In another particularly preferred Embodiment of the invention, in which glutaronitrile is used as the dicarboxylic acid dinitrile, the aqueous phase obtained in the extraction and containing glutaronitrile is used in the liquid-liquid extraction as part of a glutaronitrile production process by at least part of the otherwise in the liquid-liquid Extraction used water replaced. The glutaronitrile contained in the aqueous phase is extracted into the organic phase together with the reaction product from the production of glutaronitrile and can easily be further worked up together with this. The glutaronitrile contained in the aqueous phase is thus put to material use in an economical manner.

In a likewise preferred embodiment of the invention, the aqueous phase containing dicarboxylic acid dinitrile is used in an extraction step in a process for the production of adiponitrile. For example, it is common practice to extract the effluent from the cathode cell of an electrohydrodimerization in the presence of acrylonitrile with water in order to remove quaternary ammonium salts from the product stream and return them to the process (cf. Albright's Chemical Engineering Handbook, CRC Press, ISBN: 978-0-8247-5362-7, page 1784 ). As an example, reference is made here to a process for the production of adiponitrile, as described in US3267131 is described. Various variants of such a method are described in detail there. In a first variant, for example, the effluent from a cell for the electrohydrodimerization of acrylonitrile is diluted with acrylonitrile and water and the acrylonitrile phase that forms is then extracted in countercurrent with water in order to remove quaternary ammonium salt, which accumulates in the aqueous phase, from the reaction product, which accumulates in the acrylonitrile phase (cf. US3267131 , column 8, lines 44-56). In another variant, the effluent from the cathode cell is first extracted with acrylonitrile to produce an aqueous stream essentially free of adiponitrile and containing only the quaternary ammonium salt. The acrylonitrile stream is then extracted again with water to produce a product stream of acrylonitrile and adiponitrile essentially free of the quaternary ammonium salt (cf. US3267131 , column 9, lines 38-52). The aqueous phase obtained in the extraction of the present invention, containing a portion of the at least one dicarboxylic acid dinitrile, is outstandingly suitable for use in one of the above-described extractions of quaternary ammonium salts from the cathode liquid of an electrohydrodimerization. Dicarboxylic acid dinitrile contained in the aqueous phase passes over into the crude product and therefore does not interfere with the electrohydrodimerization.

If the dicarboxylic acid dinitrile is not adiponitrile, there are various options for proceeding further. The dicarboxylic acid dinitrile can, for example, be removed from the crude product by distillation. Since it is customary anyway to distil the crude product, the additional effort required for this is low. Alternatively, it is also possible to leave at least some of the dicarboxylic acid dinitrile in the adiponitrile and to subject it to hydrogenation together with it, in which case a diamine is formed from the dicarboxylic acid dinitrile and 1,6-hexanediamine is formed from the adiponitrile. At this point there is the possibility of separating the diamine from the 1,6-hexanediamine by distillation and further use to supply It is also conceivable to use the mixture of the two diamines, without separating them completely from one another, for the production of copolymers, ie polymers with different monomer building blocks, ie in this case two or more different diamines.

An embodiment is explained here as an example in which glutaronitrile is used as the dicarboxodinitrile for the extraction of 1,5-pentanediamine from an aqueous phase. An aqueous phase containing glutaronitrile is then obtained in the extraction, which is then in turn used in a production process for adiponitrile for a liquid-liquid extraction. In this way, as described above, quaternary ammonium salts can be separated from the catholyte and a crude product stream containing adiponitrile (from the production process for adiponitrile) and glutaronitrile (from the aqueous phase containing glutaronitrile) is obtained in this liquid-liquid extraction. Glutaronitrile and adiponitrile can be separated in the distillative processing of this crude product stream. If the two different nitriles are not separated at this point, they can be hydrogenated together to give the corresponding diamines 1,5-pentanediamine and 1,6-hexanediamine and then either separated from one another by distillation or further reacted together to form copolymers.

The embodiment of the invention in which adiponitrile is used as the dicarboxnitrile and the aqueous phase containing adiponitrile is then used in a process for preparing adiponitrile as described above is particularly preferred. In this preferred embodiment, the adiponitrile from the extraction of the diamine is converted into the crude product of the adiponitrile production and is thus sent directly to recycling. The work-up can then easily be carried out together with the adiponitrile from the process for preparing adiponitrile, and subsequent hydrogenation of the adiponitrile gives 1,6-hexanediamine as the sole main product.

The organic phase obtained after the extraction of the aliphatic diamine in the process according to the invention now contains the extracted at least one aliphatic, araliphatic or cycloaliphatic diamine and water in addition to the other, preferably the remaining, portion of the at least one dicarboxylic acid dinitrile.

Another object of the invention is an organic phase consisting of 1 to 50% by weight of at least one aliphatic, araliphatic or cycloaliphatic diamine, 0.2 to 25% by weight of water and 0.01 to 5% by weight -% of impurities, where the 100% by weight missing part of the organic phase consists of at least one dicarboxylic acid dinitrile.

Examples of impurities that can occur are salts, alkali metal or alkaline earth metal hydroxides, carbohydrates, imines, alcohols, nitro compounds, glycols, amino alcohols, carboxylic acid esters, ethers, carboxamides, monoamines, secondary amines or chlorinated hydrocarbons.

In a preferred embodiment of the invention, this organic phase, optionally after passing through one or more intermediate steps, is subjected to a hydrogenation reaction to give a hydrogenation product containing the at least one aliphatic, araliphatic or cycloaliphatic diamine. Optional intermediate steps are, for example, mixing with further dicarboxylic acid dinitrile, purification steps, drying steps or intermediate storage. Various processes are known for this hydrogenation to the corresponding diamines. If the at least one dicarboxylic acid dinitrile is an alkenyl-substituted dicarboxylic acid dinitrile, the double bond of the alkenyl group can first be hydrogenated to form the alkyl group and then the nitrile groups can be hydrogenated to form the amines. While the double bond can be hydrogenated under relatively mild conditions, for example on Pd/C, the hydrogenation of the nitrile groups requires harsher conditions and the presence of amines or ammonia. Alternatively, the double bond and the nitrile can also be hydrogenated in one step to give the corresponding alkyldiamine.

If the at least one aliphatic, araliphatic or cycloaliphatic diamine is m-xylylenediamine, it is possible to select the hydrogenation conditions in such a way that this xylylenediamine is hydrogenated at the same time to give 1,3-bis(aminomethyl)cyclohexane, which is formed, for example, by Phosgenation to 1,3-bis (isocyanatomethyl) cyclohexane (H ₆ XDI) can be implemented.

Out US3696153A is the hydrogenation of adiponitrile at temperatures of 100 to 200 °C and a pressure of about 340 atm (cf. column 3, lines 20-32) in the presence of ammonia over an iron-containing catalyst (cf. column 2, lines 19-27 ) known. Similar procedures can also be found in US4064172 (cf. column 2, lines 20-30).

In US3255248 also describes a catalytic hydrogenation process with which preferably hydrocarbon-based nitriles having 2-20 carbon atoms and 1 or 2 nitrile groups (cf. column 2, lines 11-14) can be hydrogenated to the corresponding amines. The process is carried out at 40-250°C and a pressure above 20 atm (cf. column 2, lines 40-69). Sintered metal catalysts based on nickel and/or cobalt are used as catalysts (cf. column 3, lines 1-21).

In US3232888 describes the use of cobalt-based catalysts for the hydrogenation of nitriles or dinitriles in liquid ammonia. Example 1 shows that the hydrogenation also works in the presence of larger amounts of the product of the hydrogenation, in this case 1,6-hexanediamine. Example 2 describes the hydrogenation of 1,8-octanedinitrile.

Another important method for hydrogenating dicarboxylic acid dinitriles is, for example, in DE69413560T2 described and uses doped Raney nickel based catalysts (see last three paragraphs on page 7). The hydrogenation proceeds in the presence of an alkali metal hydroxide (see page 8, paragraph 3), up to 50% water (see page 8, paragraph 6) and the desired amine (cf. page 9, paragraph 3) under relatively mild conditions, ie at a temperature below 150 °C, preferably below 100 °C (cf. page 9, last 2 paragraphs) and a hydrogen pressure of 1 to 100 bar (cf Page 10, paragraph 1). 80° C. and 2.5 MPa of hydrogen are disclosed as examples (page 11f, example 2).

In a preferred embodiment of the process according to the invention, the organic phase from the extraction, which contains a further subset, preferably the remaining subset, of the at least one dicarboxylic acid dinitrile used as extraction agent and the at least one aliphatic, araliphatic or cycloaliphatic diamine extracted from the aqueous phase, undergoes a hydrogenation reaction subjected to at least partially converting the at least one dicarboxylic acid dinitrile into the corresponding diamine. Preferably ≧80%, particularly preferably ≧95% and very particularly preferably ≧97% of the at least one dicarboxylic acid dinitrile are converted into the corresponding diamine in the hydrogenation reaction. The hydrogenation reaction is preferably carried out over a catalyst based on Raney nickel, since these catalysts are known to tolerate very well higher levels of amine and water, which is generally also present in the organic phase from the extraction. The extracted at least one aliphatic, araliphatic or cycloaliphatic diamine and the second diamine formed from the hydrogenation of the at least one dicarboxylic acid dinitrile are finally subjected to further purification.

In a particularly preferred embodiment, the at least one dicarboxylic acid dinitrile is chosen such that during the hydrogenation at least some of the dicarboxylic acid dinitrile is converted into the same amine that was extracted from the aqueous phase. For example, adiponitrile is used as the extraction agent if the aqueous phase contains 1,6-hexanediamine, glutaronitrile if it contains 1,5-pentanediamine, or 2-methylglutaronitrile or 2-methyleneglutaronitrile if it contains 1,5-diamino-2- contains methylpentane. In this way it is achieved that only one diamine is obtained as the main product in the hydrogenation, so that there is no need for a complicated separation of different diamines during the purification of the products.

The products from the hydrogenation of the at least one dicarboxylic acid dinitrile in the presence of the at least one aliphatic diamine are purified by processes known per se to those skilled in the art. In general, purification is carried out by distillation in one or more distillation columns. It is particularly advantageous here that the previously extracted at least one aliphatic, araliphatic or cycloaliphatic diamine is likewise subjected to the reduction conditions of the hydrogenation during the hydrogenation of the dicarboxylic acid dinitrile without further action. In this way, any polarographically reducible compounds present can be at least partially degraded and separated off in the subsequent purification, which has a positive effect on the product quality of the diamine and the polymers produced therefrom and counteracts discoloration of the polymers. Such an effect is, for example, in EP3235804A1 described for a catalytic hydrogenation of 1,5-pentanediamine containing 2,3,4,5-tetrahydropyridine, the 2,3,4,5-tetrahydropyridine in piperidine converted and, if necessary, removed in a subsequent distillation [paragraphs 39-42].

In a further preferred embodiment of the invention, the diamine obtained in the hydrogenation, optionally after passing through one or more intermediate steps, is reacted with phosgene to form a diisocyanate. Optional intermediate steps are, for example, cleaning steps, drying steps or intermediate storage. If it is a mixture of different diamines, i.e. the dicarboxylic acid dinitrile was selected in such a way that the product of its hydrogenation does not correspond to the at least one aliphatic, araliphatic or cycloaliphatic amine to be extracted, or simply a mixture of different dicarboxylic acid dinitriles and/or different diamines was used, it is possible to react this mixture of diamines with phosgene to give the diisocyanate, but it is preferred to separate the mixture before the phosgenation, for example in a distillation, and then to react individual diamines with phosgene.

The phosgenation of the diamine can take place, for example, in the gas phase. To this end, the diamine is preferably vaporized and heated to a temperature within the temperature range from 200 to 600.degree. Optionally, the vaporization and also the use of the diamine vapors generated during the vaporization take place in the presence of an inert gas and/or vapors of an inert solvent. The preferred inert gas is nitrogen. Examples of suitable inert solvents are chlorobenzene, o-dichlorobenzene, xylene, chloronaphthalene or mixtures thereof.

The phosgene used in the phosgenation is preferably used in excess, based on the amino groups. In general, an amount of phosgene which corresponds to 150 to 350% of theory with regard to the phosgenation reaction taking place is sufficient. The phosgene stream is preferably heated to a temperature within the range of 200 to 600°C prior to reaction.

To carry out the phosgenation, the preheated, diamine-containing stream and the likewise preheated phosgene stream are preferably fed continuously into a cylindrical reaction chamber and mixed with one another there. Suitable cylindrical reaction spaces are, for example, tube reactors, which generally consist of steel, glass, alloyed or enamelled steel. They are generally of a length which is sufficient to allow complete reaction of the amine with the phosgene under the process conditions. Furthermore, the dimensions of the reaction space are preferably chosen such that a turbulent flow with a Reynolds number of at least 2500 prevails in the reaction space. This is generally guaranteed when the flow speed is more than 90 m/s. Such a flow rate can be ensured by setting a corresponding differential pressure between the product lines to the reaction space and the outlet from the reaction space. In general, the pressure in the feed lines is 200 to 300 mbar(g) and at the outlet from the reaction chamber 150 to 200 mbar(g).

After the phosgenation reaction has taken place in the reaction space, the mixture continuously leaving the reaction space is preferably freed from the diisocyanate formed. This can be done, for example, by selective condensation in an inert solvent such as, for example, chlorobenzene or dichlorobenzene. If the diamine-containing stream already contained an inert solvent, preference is given to using the same solvent here. The temperature of the solvent is preferably selected so that on the one hand it is above the decomposition temperature of the carbamic acid chloride corresponding to the diisocyanate and on the other hand the diisocyanate condenses or dissolves in the solvent, while phosgene, hydrogen chloride and, if appropriate, inert gas pass through the condensation stage in gaseous form. Solvent temperatures in the range from 120 to 200° C. are particularly suitable. The resulting crude diisocyanate solution is then processed into pure diisocyanate in a multi-stage distillation process.

The gas mixture passing through the condensation stage to obtain the at least one diisocyanate is then preferably freed from excess phosgene in a manner known per se. This can be done by means of a cold trap, absorption in an inert solvent (e.g. chlorobenzene (MCB), or dichlorobenzene (ODB) kept at a temperature of -10 °C to 8 °C) or by adsorption and hydrolysis on activated carbon Hydrogen chloride gas passing through can preferably be oxidized to chlorine in a manner known per se and then, for example, converted back to phosgene.

In a further embodiment, the phosgenation of the diamine takes place in the liquid phase. The reaction can then be carried out in a number of ways. Either the diamine is reacted directly with phosgene in an inert liquid medium (base phosgenation) or the diamine is first converted into the corresponding salt by reaction with hydrogen chloride gas or carbon dioxide in an inert liquid medium and then reacted with phosgene (hydrochloride or carbamic acid phosgenation). In particular, chlorobenzene and/or dichlorobenzene are suitable liquid mediums for all phosgenations.

In base phosgenation, the reaction is carried out in two stages in the inert liquid medium. In the first stage, the cold phosgenation, the temperature of the reaction mixture is preferably kept in a range between 0 and 100°C. A suspension is formed which contains carbamic acid chloride, amine hydrochloride and small amounts of free diisocyanate. A solution of phosgene in an inert solvent is preferably initially taken and then a solution or suspension of the amine in the same solvent and, if appropriate, further phosgene are added. In this way, the concentration of free amine is kept low and the undesired formation of ureas is suppressed.

In the second stage, hot phosgenation, the temperature is increased and is preferably in the range from 120 to 200°C. It is maintained in this range while further phosgene is fed in until the conversion to the diisocyanate is complete, ie the evolution of HCl comes to a standstill. Expediently, phosgene is used in excess. If required, the reaction can be carried out both in the cold and in the hot phosgenation with the introduction of an inert gas.

In amine hydrochloride or carbamic phosgenation, the amine is preferably first reacted with hydrogen chloride gas or carbon dioxide in an inert liquid medium to produce the corresponding salt. The reaction temperature during this salt formation is preferably in a range from 0 to 80°C. This is followed by the phosgenation step as the second step, which is essentially similar to the hot phosgenation from the base phosgenation described above. Here, too, the temperature is preferably kept in the range from 120 to 200° C. while phosgene and optionally an inert gas are introduced into the reaction mixture. The introduction continues until the conversion to the diisocyanate is complete. Here, too, phosgene is preferably used in excess in order to accelerate the reaction.

Both in the base phosgenation and in the amine hydrochloride or carbamic phosgenation, the remaining phosgene and hydrogen chloride gas are preferably blown out with an inert gas, preferably with nitrogen, after the reaction has ended. If necessary, filtration can be carried out to remove any solids present, such as unreacted amine hydrochlorides. The diisocyanate formed is then processed into the pure diisocyanate in a multi-stage distillation process.

In a further preferred embodiment, the hydrogenation product is reacted with a dicarboxylic acid and/or a dicarboxylic acid derivative to form a polyamide, with or without going through one or more intermediate steps. In this embodiment, the diamine is preferably heated in aqueous solution together with a dicarboxylic acid, optionally after passing through one or more intermediate steps, and is thus converted into the polyamide in a polycondensation reaction. Optional intermediate steps are, for example, cleaning steps or intermediate storage. If it is a mixture of different diamines, i.e. the dicarboxylic acid dinitrile was selected in such a way that the product of its hydrogenation does not correspond to the at least one aliphatic, araliphatic or cycloaliphatic amine to be extracted, or simply a mixture of different dicarboxylic acid dinitriles and/or different diamines was used, this mixture can optionally be separated into the individual diamines before the polycondensation or used as such to form copolymers.

In an embodiment that is alternatively preferred to the above paragraph, the hydrogenation product is reacted with at least one epoxy resin, with or without going through one or more intermediate steps. In this process, compounds containing epoxide groups are reacted with the diamine obtained in the hydrogenation to form duroplastics. The reaction particularly preferably takes place as cold curing at room temperature.

Another subject of the invention is the use of at least one dicarboxylic acid dinitrile for the extraction of at least one aliphatic, araliphatic or cycloaliphatic diamine from a mixture containing at least 40% by weight of water and 0.2 to 40% by weight of the at least one aliphatic, araliphatic or cycloaliphatic Diamine to obtain an aqueous phase containing water and a portion of the at least one dicarboxnitrile and an organic phase containing a further, preferably the remaining portion of the at least dicarboxnitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine.

A preferred embodiment of the process is the use of 2-methylglutaronitrile and/or 2-methyleneglutaronitrile to extract 1,5-diamino-2-methylpentane from an aqueous phase containing 1,5-diamino-2-methylpentane.

Another preferred embodiment of the method is the use of glutaronitrile to extract 1,5-pentanediamine from an aqueous phase containing 1,5-pentanediamine.

Another preferred embodiment of the process is the use of succinonitrile to extract 1,4-butanediamine from an aqueous phase containing 1,4-butanediamine.

Another preferred embodiment of the method is the use of adiponitrile to extract 1,6-hexanediamine from an aqueous phase containing 1,6-hexanediamine.

Another subject of the invention is the use of the organic phase containing a further subset, preferably the remaining subset, of the at least one dicarboxylic acid dinitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine as feedstock in a hydrogenation to produce an aliphatic diamine or a mixture of aliphatic diamines.

A particularly advantageous process according to the invention is explained below by way of example:
Biochemically, 1,5-pentanediamine is produced by decarboxylation of L-lysine. Cellular components are first removed from the fermentation broth by filtration, so that an aqueous mixture containing about 20% by weight of 1,5-pentanediamine is obtained. This mixture is adjusted to pH 11 by adding sodium hydroxide and extracted with glutaronitrile at 25° C. in countercurrent in a multi-stage extraction column. An aqueous stream containing about 10% by weight falls at one end of the extraction column. glutaronitrile and 0.08% by weight of pentanediamine. At the other end of the extraction column is an organic phase containing glutaronitrile, 1,5-pentanediamine and about 10% by weight of water.

The aqueous stream from the extraction is provided to a process to produce glutaronitrile by reacting 1,3-dichloropropane with potassium cyanide. This process includes a purification step in which the reaction mixture is extracted with water and chloroform and the aqueous stream from the extraction replaces part of the water here. The glutaronitrile is also recovered from the aqueous stream and then further processed together with the glutaronitrile from the reaction of the 1,3-dichloropropane.

The organic phase containing glutaronitrile, about 25 wt .-% 1,5-pentanediamine and about 10 wt .-% water is then according to the teaching of DE69413560T2 a catalytic hydrogenation using a titanium-doped Raney nickel catalyst at 80 ° C and 20 bar hydrogen pressure hydrogenated. Under these conditions, the glutaronitrile is completely converted to 1,5-pentanediamine and traces of polarographically reducible compounds are also reduced, for example 2,3,4,5-tetrahydropyridine to piperidine. The product of the hydrogenation reaction is purified in a vacuum distillation and 1,5-pentanediamine is obtained in a quality suitable for the production of 1,5-pentanediisocyanate by phosgenation. This product is subjected to a gas phase phosgenation as in EP3194362 described and, after purification by distillation, 1,5-pentane diisocyanate is obtained.

Claims (15)

Process for obtaining at least one aliphatic, araliphatic or cycloaliphatic diamine from a mixture containing at least 35% by weight of water and 0.2 to 60% by weight of the at least one aliphatic, araliphatic or cycloaliphatic diamine by extraction of the at least one aliphatic, araliphatic or cycloaliphatic diamine with at least one dicarboxylic acid dinitrile to obtain an aqueous phase containing water and a portion of the at least one dicarboxylic acid dinitrile and an organic phase containing a further portion of the at least one dicarboxylic acid dinitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine. The method according to claim 1, characterized in that the at least one dicarboxylic acid dinitrile is a dicarboxylic acid dinitrile according to the formula (I),

NC-R-CN (I),

where R is an alkyl group having 1 to 12 carbon atoms, or an alkenyl group having 4 to 8 carbon atoms, or an aryl group having 6 carbon atoms. Process according to one of Claims 1 or 2, characterized in that the at least one dicarboxylic acid dinitrile is selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, methylglutaronitrile, ethylsuccinonitrile and methyleneglutaronitrile. Process according to one of Claims 1 to 3, characterized in that the mixture has a content of at least one aliphatic, araliphatic or cycloaliphatic diamine of ≤ 40% by weight and ≥ 0.5% by weight, based on the total mass of the mixture , having. Process according to one of Claims 1 to 4, characterized in that the at least one aliphatic, araliphatic or cycloaliphatic diamine is selected from the group consisting of 1,4-butanediamine, neopentanediamine, 1,5-pentanediamine, 1,5-diamino-2 -methylpentane, 1,5-diamino-2-butyl-2-ethylpentane, 1,6-hexanediamine, 2,5-diamino-2,5-dimethylhexane, 1-amino-3,3,5-trimethyl-5-aminomethyl -cyclohexane, 1,4-diaminocyclohexane, 2,4-diamino-1-methylcyclohexane, 2,6-diamino-1-methylcyclohexane, m-hexahydroxylylenediamine, 1,6-diamino-2,2,4-trimethylhexane, 1,6 -Diamino-2,4,4-trimethylhexane, 2,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, bis(aminomethyl)bicyclo[2.2.1]heptane, 1,8-diaminooctane, 1,9-diaminononane, 1 ,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane and m-xylylenediamine. Process according to one of Claims 1 to 5, characterized in that the extraction takes place in an alkaline medium. The method according to any one of claims 1 to 6, characterized in that the organic phase containing the further, preferably the remaining portion of the at least one dicarboxylic acid dinitrile and the extracted at least one aliphatic, araliphatic or cycloaliphatic diamine and water, optionally after passing through one or more intermediate steps, a hydrogenation reaction to obtain a hydrogenation product containing at least one aliphatic, araliphatic or cycloaliphatic diamine is subjected. Process according to Claim 7, characterized in that the at least one dicarboxylic acid dinitrile is selected in such a way that in the hydrogenation at least part of the dicarboxylic acid dinitrile is converted into the same diamine which was extracted from the aqueous phase. Process according to Claim 7 or 8, characterized in that the hydrogenation product is reacted with phosgene to form a diisocyanate, with or without passing through one or more intermediate steps. Process according to Claim 7 or 8, characterized in that the hydrogenation product is reacted with a dicarboxylic acid and/or a dicarboxylic acid derivative to give a polyamide, with or without going through one or more intermediate steps. Process according to Claim 7 or 8, characterized in that the hydrogenation product is reacted with at least one epoxy resin, with or without going through one or more intermediate steps. Use of at least one dicarboxylic acid dinitrile for the extraction of at least one aliphatic, araliphatic or cycloaliphatic amine from a mixture containing at least 35% by weight of water and 0.2 to 60% by weight of the at least one aliphatic, araliphatic or cycloaliphatic diamine to obtain an aqueous phase Water and a portion of the at least one dicarboxylic acid dinitrile and an organic phase containing a further portion, preferably the remaining portion, of the at least one dicarboxylic acid dinitrile and the at least one aliphatic, araliphatic or cycloaliphatic diamine. Use of the organic phase containing a further subset, preferably the remaining subset, of the at least one dicarboxylic acid dinitrile and the at least an aliphatic, araliphatic or cycloaliphatic diamine as feedstock in a hydrogenation to produce an aliphatic diamine. Organic phase obtainable or produced in a process according to any one of claims 1 to 6, containing a further subset, preferably the remaining subset, of the at least one dicarboxylic acid dinitrile, the at least one aliphatic, araliphatic or cycloaliphatic diamine and water. Organic phase consisting of 1 to 50% by weight of at least one aliphatic, araliphatic or cycloaliphatic diamine, 0.2 to 25% by weight of water and 0.01 to 5% by weight of impurities, the 100% by weight of the missing part of the organic phase consists of at least one dicarboxylic acid dinitrile.